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36 The PCB Magazine • October 2014 PCBS FOR AUTOMOBILES: WHAT TO WEAR TO THE PARTY? continues push automakers into previously untouched technologies due to the component footprints for these capabilities. As such, in order to capture a piece of this market segment many fabricators will have to ramp up their capa- bilities for fine lines, higher layer counts, and microvias. • Drilling Microvias: Drilling small holes is one thing to master, but drilling small blind vias is a totally different chapter in the book. Most folks assume that both an expensive and time-consuming outsource is involved, or they'll have to spend $500k on a laser drill. However, it's important not to overlook the ad- vancements that have been made in mechani- cal drilling systems. The incorporation of linear motors and scales and refined contact drilling systems enable you to drill diameters down to 0.002", with positional and Z-axis accuracy of 0.0005". This is more than adequate for most designs at less than half the cost of a laser drill. Furthermore, unlike a laser drill, when the me- chanical drill isn't busy drilling blind microvias it can be commissioned to drill standard prod- ucts to enhance its ROI. • Microvia Drill Quality: When it comes to consumable materials in the drill room, the habit for most fabricators is to go with the cheapest possible materials since they are dis- carded after just a single use. However, backup and entry quality are paramount when it comes to successful microvia creation. Using coated backup with high-quality pressed fiber will en- sure reduced burring and minimal debris pull- back into the hole. It's much easier to clean a hole out if there is less debris in it to begin with. Additionally, using the proper mix of phenolic, aluminum, and coated entry for each specific application will maximize location accuracy and drill bit life. • Layer to Layer Registration: For most folks, this means investing in new tooling sys- tems that have more pins to ensure greater layer-to-layer accuracy. Depending upon the current state of your tooling, this may not be necessary. The first step would be to check the condition of what you have already. Often, huge gains can be made just by checking the straightness of your pins, quality of your bush- ings, and flatness of your caul and lamination plates. The next step would focus on pre-engi- neering. Higher-technology PCBs often incor- porate the use of thin cores and mixed copper weights that result in non-uniform stackups. With a non-uniform stackup you can no longer count on all of the cores shrinking or expand- ing at the same rate that you can correct for in drilling. We've found tools such as X-ray drills and PerfecTest to be invaluable at providing data to continuously tighten your process and scale factors. figure 2: automotive PCb categories and the changes in peak temperature between the five classes of automotive PCbs.